2.4 Monitoring Faults

Outline

Devices that Monitor Faults

• the geologists use machines to remember how the ground moves during an earthquake
  • to look closely at the differences in the ground, geologists put machines in the ground that tell if there is tension (stress) and if the ground starts to deform
  • sadly, earthquakes usually start without any notice
    • the only hint about an incoming earthquake is the little ascend or descend in the elevation or the slant of ground
      • the machines that geologists use to observe these motions are creep meters,laser ranging devices, tiltmeters, and satellites

Creep Meters

• a creep meter uses a wire extended across a fault to measure the horizontal proposition of the earth on one side of a fault, the wire is tied to a pole on the other side of the fault, the wire is stuck onto a heavy item that can slide if the fault makes any movement.
  • geologists can see how much the fault has moved by taking a measurement of how much the heavy object has moved against the fault

Laser-Ranging Devices

• a laser-ranging device uses a laser beam to find any small changes in the fault
  • this instrument measures the difference in the time that takes the laser beam to get to the reflector and return
    • this gadget can find any difference in the length to the reflector

Tiltmeters

• it measures if there is any tilting on the ground
  • it uses to bulbs that are filled with liquid and is connected by a hollow stem
  • it can tell if the land rises or falls

Satellite Monitors

• a satellite that bounces radio waves off the ground to detect if there's any change on the earth's surface
• it can also take pictures of the ground surface to look if there are any changes on the earth's surface

Monitoring Risk in the United States

• geologists can't predict when and where and earthquake will happen
• geologists are able to tell where earthquakes will likely happen
  • by studying where active faults are
  • by studying where past earthquakes have occurred
    • the highest rick of earthquakes are
      • along the Pacific coast of the states in California, Washington, and Alaska
        • the reason why the risk is so high here is because this is where the Pacific and North America plates meet
          • some very dangerous earthquakes occur on the east of the Rocky Mountains